THE CAMPANULAEID^ AND THE BONNEVIBLLID^. d 



Many species present the character of a simple rootstock from wliich spring undivided 

 pedicels each bearing its goblet-shaped hydrotheca. The rootstocks themselves twine irregu- 

 larly around the branches of other hydroids, algae, and whatever other support may be available. 

 In the genera Campanularia, Olytia (fig. 1), and Ohelia these cHmbing rootstocks are usually 

 quite iiTegu^ar in their course. In Orthopyxis and Silicularia the algse form the favorite means 

 of support, and sometimes the rootstocks cover the surface of the broad leaves of Laminaria, 

 for instance, with a reticulate pattern which is at times fairly regular {Orthopyxis clytioides 



CHEEPING ROOTSTOCK OF THE CAMPANULARID^. 



Fig. 1. — Clytia sargassicola. 



Fig. 2. — Orthopyxis clytioides. (After Hartlaub.) 



Fig. 3. — Campanularia urceolata. 



(fig. 2) or Silicularia reticularia) . At other times the leaves of Laminaria are traversed by 

 bands of parallel rootstocks closely appressed together as in Silicularia rosea. 



Again there are rootstocks that are closely and regularly annulated throughout and others 

 that are smooth throughout; while still others combine these conditions, as in the case of Or- 

 thopyxis caliculata, where both the annulated and the smooth rootstocks are found in the 

 same specimen. Torreyhas noticed this in Campanularia urceolata (fig. 3) — 



A fact of some interest is the beautiful spiral annulation which appears on the hydrorhiza whenever it happens 

 to grow for a space without touching the substratum. It seems clear that this striking heteromorphosis, and the 

 change of form of the perisarc of the stolon are casually related to the presence or absence of a contact stimulus.' 



I have noticed the same thing in the case of Campanularia speciosa Clark. 

 These creeping stolons appear to adhere to the substratum over which they grow by means 

 of the adhesive quality of the perisarc rather than by sending out rootlets, as in many climbing 



' The Hydroida of the Pacific Coast, 1902, p. 54. 



